(function (window) {
  const l = 42, // 滑块边长
      r = 10, // 滑块半径
      w = 310, // canvas宽度
      h = 155, // canvas高度
      PI = Math.PI
  const L = l + r * 2 // 滑块实际边长

  function getRandomNumberByRange(start, end) {
      return Math.round(Math.random() * (end - start) + start)
  }

  function createCanvas(width, height) {
      const canvas = createElement('canvas')
      canvas.width = width
      canvas.height = height
      return canvas
  }

  function createImg(onload) {
      const img = createElement('img')
      img.crossOrigin = "Anonymous"
      img.onload = onload
      img.onerror = () => {
          img.src = getRandomImg()
      }
      img.src = getRandomImg()
      return img
  }

  function createElement(tagName) {
      return document.createElement(tagName)
  }

  function addClass(tag, className) {
      tag.classList.add(className)
  }

  function removeClass(tag, className) {
      tag.classList.remove(className)
  }

  function getRandomImg() {
      return 'https://picsum.photos/300/150/?image=' + getRandomNumberByRange(0, 1084)
  }

  function draw(ctx, operation, x, y) {
      ctx.beginPath()
      ctx.moveTo(x, y)
      ctx.lineTo(x + l / 2, y)
      ctx.arc(x + l / 2, y - r + 2, r, 0, 2 * PI)
      ctx.lineTo(x + l / 2, y)
      ctx.lineTo(x + l, y)
      ctx.lineTo(x + l, y + l / 2)
      ctx.arc(x + l + r - 2, y + l / 2, r, 0, 2 * PI)
      ctx.lineTo(x + l, y + l / 2)
      ctx.lineTo(x + l, y + l)
      ctx.lineTo(x, y + l)
      ctx.lineTo(x, y)
      ctx.fillStyle = '#fff'
      ctx[operation]()
      ctx.beginPath()
      ctx.arc(x, y + l / 2, r, 1.5 * PI, 0.5 * PI)
      ctx.globalCompositeOperation = "xor"
      ctx.fill()
  }

  function sum(x, y) {
      return x + y
  }

  function square(x) {
      return x * x
  }

  class SlidingVerificationCode {
      constructor(el, success, fail) {
          this.el = el
          this.success = success
          this.fail = fail
      }

      init() {
          this.initDOM()
          this.initImg()
          this.draw()
          this.bindEvents()
      }

      initDOM() {
          const fathers = createElement('div')//父级
          const canvas = createCanvas(w, h) // 画布
          const block = canvas.cloneNode(true) // 滑块
          const sliderContainer = createElement('div')
          const refreshIcon = createElement('div')
          const sliderMask = createElement('div')
          const slider = createElement('div')
          const sliderIcon = createElement('span')
          const text = createElement('span')

          fathers.className='fatherBox';
          fathers.style='';
          canvas.className='myCanvas';
          block.className = 'block';
          sliderContainer.className = 'sliderContainer';
          refreshIcon.className = 'refreshIcon';
          sliderMask.className = 'sliderMask';
          slider.className = 'slider';
          sliderIcon.className = 'sliderIcon';
          text.innerHTML = '向右滑动滑块填充拼图';
          text.className = 'sliderText';
          const el = this.el;
          //el.appendChild(canvas)
          //el.appendChild(refreshIcon)
          //el.appendChild(block)
          fathers.appendChild(canvas)
          fathers.appendChild(refreshIcon)
          fathers.appendChild(block)
          el.appendChild(fathers)
          slider.appendChild(sliderIcon)
          sliderMask.appendChild(slider)
          sliderContainer.appendChild(sliderMask)
          sliderContainer.appendChild(text)
          el.appendChild(sliderContainer)

          Object.assign(this, {
              canvas,
              block,
              sliderContainer,
              refreshIcon,
              slider,
              sliderMask,
              sliderIcon,
              text,
              canvasCtx: canvas.getContext('2d'),
              blockCtx: block.getContext('2d')
          })
      }

      initImg() {
          const img = createImg(() => {
              this.canvasCtx.drawImage(img, 0, 0, w, h)
              this.blockCtx.drawImage(img, 0, 0, w, h)
              const y = this.y - r * 2 + 2
              const ImageData = this.blockCtx.getImageData(this.x, y, L, L)
              this.block.width = L
              this.blockCtx.putImageData(ImageData, 0, y)
          })
          this.img = img
      }

      draw() {
          // 随机创建滑块的位置
          this.x = getRandomNumberByRange(L + 10, w - (L + 10))
          this.y = getRandomNumberByRange(10 + r * 2, h - (L + 10))
          draw(this.canvasCtx, 'fill', this.x, this.y)
          draw(this.blockCtx, 'clip', this.x, this.y)
      }

      clean() {
          this.canvasCtx.clearRect(0, 0, w, h)
          this.blockCtx.clearRect(0, 0, w, h)
          this.block.width = w
      }

      bindEvents() {
          this.el.onselectstart = () => false
          this.refreshIcon.onclick = () => {
              this.reset()
          }

          let originX, originY, trail = [], isMouseDown = false
          this.slider.addEventListener('touchstart', function (e) {

            if (e.targetTouches.length == 1) { 
                var touch = e.targetTouches[0]; 
                originX = touch.pageX, originY = touch.pageY
                isMouseDown = true
            }

              
          })
          document.addEventListener('touchmove', (e) => {
              if (!isMouseDown) return false
              if (e.targetTouches.length == 1) { 
                var touch = e.targetTouches[0]; 
                const moveX = touch.pageX - originX
                const moveY = touch.pageY - originY
                if (moveX < 0 || moveX + 38 >= w) return false
                this.slider.style.left = moveX + 'px'
                var blockLeft = (w - 40 - 20) / (w - 40) * moveX
                this.block.style.left = blockLeft + 'px'

                addClass(this.sliderContainer, 'sliderContainer_active')
                this.sliderMask.style.width = moveX + 'px'
                trail.push(moveY)
              }
          })
          document.addEventListener('touchend', (e) => {
              if (!isMouseDown) return false
              isMouseDown = false
              if (e.x == originX) return false
              removeClass(this.sliderContainer, 'sliderContainer_active')
              this.trail = trail
              const {spliced, TuringTest} = this.verify()
              if (spliced) {
                  if (TuringTest) {
                      addClass(this.sliderContainer, 'sliderContainer_success')
                      this.success && this.success()
                  } else {
                      addClass(this.sliderContainer, 'sliderContainer_fail')
                      this.text.innerHTML = '再试一次'
                      this.reset()
                  }
              } else {
                  addClass(this.sliderContainer, 'sliderContainer_fail')
                  this.fail && this.fail()
                  setTimeout(() => {
                      this.reset()
                  }, 1000)
              }
          })
      }

      verify() {
          const arr = this.trail // 拖动时y轴的移动距离
          const average = arr.reduce(sum) / arr.length // 平均值
          const deviations = arr.map(x => x - average) // 偏差数组
          const stddev = Math.sqrt(deviations.map(square).reduce(sum) / arr.length) // 标准差
          const left = parseInt(this.block.style.left)
          return {
              spliced: Math.abs(left - this.x) < 10,
              TuringTest: average !== stddev, // 只是简单的验证拖动轨迹，相等时一般为0，表示可能非人为操作
          }
      }

      reset() {
          this.sliderContainer.className = 'sliderContainer'
          this.slider.style.left = 0
          this.block.style.left = 0
          this.sliderMask.style.width = 0
          this.clean()
          this.img.src = getRandomImg()
          this.draw()
      }

  }

  window.SlidingVerificationCode = {
      init: function (el, success, fail) {
          new SlidingVerificationCode(el, success, fail).init()
      }
  }
}(window))